[...]

my @failed = [];

foreach my $host (@host) {
   print "$host is ";
   unless ($ping->ping($host, $first)) {
      sleep ($delay);
      unless ($ping->ping($host, $second)) {
         push @failed, $host;
         print 'NOT ';
      }
   }
   print "reachable.\n";
 }

notify(@failed) if @failed;

[...]